Someone in the Axiom thread got Ixion and Axiom confused, and suggested we start a thread specifically for the Ixion concept being developed by NanoRacks, ULA, and MDA. I did a quick search and found a few mentions of Ixion in other threads (one thread on an article about the NextSTEP BAA Ph2 that this study is part of, and one on the NanoRacks thread), but I think it might be worth having a dedicated thread for their specific "wet station" concept.

IIRC there have been a few articles posted describing more about what NanoRacks' team is looking at here, including doing a node module made from Centaur domes and forward skirt structures that would allow kitting out a Centaur after it gets to ISS. If people can track those down, it would probably be worth relinking to them here in this thread.

All told, I think this is an interesting concept for getting large amounts of inexpensive pressurized volume in space. Most people assume that Bigelow's inflatables, or traditional ISS modules are the only ways to go for commercial space facilities, but I think there's a place for wet habitats (or Skylab like dry habitats) in the future, so I wanted to start a dedicated Ixion thread.

Anthony Colangelo's Podcast Main Engine Cutoff has a really interesting interview with Mike Johnson the chief designer for Nanoracks on this, really worth a listen:https://mainenginecutoff.com/podcast/20

Mike Johnson: ... The reason that Skylab wasn't build like this is kind of a strange story: [NASA] had fewer Saturn IBs than they had Saturn Vs, so von Braun just decided to use a Saturn V and fly up a "dry" lab, with all of the equipment aboard it already.

IEEE Spectrum: So you're saying that NASA didn't go with the idea of reusing a wet Saturn 1B stage for Skylab mostly because they had spare Saturn Vs lying around that could lift an entire dry lab all at once?

Personally I feel that the concept is weak in LEO for anything more than initial testing, but much stronger in higher deltaV destinations or within gravity wells where crude in-situ resources are available but pressurized volume is at a premium. For example multiple Xeus landers could be tied together on the lunar surface providing a larger pressurized volume for anything from living areas to propellant storage. The relative cost of getting the hardware in place on lunar surface should far eclipse the value in returning said hardware to a staging orbit for reuse.

And even if it was plausible, I would think that Centaur - with its A) incredible mass fraction, B) very thin tank skin, and C) thin diameter - would be far from the optimal starting point.

I'm not sure what tank skin thickness has to do with it. You're obviously going to need some sort of MMOD protection, even if you had a thick isogrid tank wall. The smaller diameter is less optimal, but the techniques they develop for Centaur should work for ACES too, and that's 2/3 the volume of a bigelow module.

For human habitat a wet habitat may have its limits, but for low cost robotic factory it could be ideal. Nanoracks and SSL are looking at this as basis for in orbit manufacturing. Add Made In Space to equation and lot possibilities open up.

For human habitat a wet habitat may have its limits, but for low cost robotic factory it could be ideal. Nanoracks and SSL are looking at this as basis for in orbit manufacturing. Add Made In Space to equation and lot possibilities open up.

Ideal? It's as ideal as setting up a machine shop in an old tanker truck on Earth.

And even on Earth even the most robotic of factories aren't sealed-off black boxes that humans never enter. Robotic manufacturing requires regular maintenance by humans. So there's no way with today's technology that a factory in space doesn't have to be a human habitat.

For human habitat a wet habitat may have its limits, but for low cost robotic factory it could be ideal. Nanoracks and SSL are looking at this as basis for in orbit manufacturing. Add Made In Space to equation and lot possibilities open up.

Ideal? It's as ideal as setting up a machine shop in an old tanker truck on Earth....

To put the alegory in it's context, it is as ideal as setting up a machine shop in an old tanker truck you got for free, instead of buying a brand-new tanker truck and flying it to space...

For human habitat a wet habitat may have its limits, but for low cost robotic factory it could be ideal. Nanoracks and SSL are looking at this as basis for in orbit manufacturing. Add Made In Space to equation and lot possibilities open up.

Ideal? It's as ideal as setting up a machine shop in an old tanker truck on Earth....

To put the alegory in it's context, it is as ideal as setting up a machine shop in an old tanker truck you got for free, instead of buying a brand-new tanker truck and flying it to space...

Still not ideal though

You still need to fly all the people and equipment to space to convert the old tank into a factory or whatever. If those people doing the conversion are going to require a lot of time in space and support equipment, the whole conversion process might require a lot more to be launched into space than the alternative of just launching a module that is already designed and built on Earth to be the desired factory (or habitat or whatever).

Remember, this conversion has to be done in space. Upper stages don't have airlocks or docking ports or anything like that. Are you going to cut a hole in the space for a docking adapter and weld it in place in vacuum in zero-g? Is the structure of the upper stage even going to be compatible with that kind of a change?

It's all far more ambitious than anything that's ever been attempted in space before, and all to avoid a solved problem: just launching something into space that's already exactly the factory or habitat you want.

For human habitat a wet habitat may have its limits, but for low cost robotic factory it could be ideal. Nanoracks and SSL are looking at this as basis for in orbit manufacturing. Add Made In Space to equation and lot possibilities open up.

Ideal? It's as ideal as setting up a machine shop in an old tanker truck on Earth....

To put the alegory in it's context, it is as ideal as setting up a machine shop in an old tanker truck you got for free, instead of buying a brand-new tanker truck and flying it to space...

Still not ideal though

You still need to fly all the people and equipment to space to convert the old tank into a factory or whatever. If those people doing the conversion are going to require a lot of time in space and support equipment, the whole conversion process might require a lot more to be launched into space than the alternative of just launching a module that is already designed and built on Earth to be the desired factory (or habitat or whatever).

Remember, this conversion has to be done in space. Upper stages don't have airlocks or docking ports or anything like that. Are you going to cut a hole in the space for a docking adapter and weld it in place in vacuum in zero-g? Is the structure of the upper stage even going to be compatible with that kind of a change?

It's all far more ambitious than anything that's ever been attempted in space before, and all to avoid a solved problem: just launching something into space that's already exactly the factory or habitat you want.

For human habitat a wet habitat may have its limits, but for low cost robotic factory it could be ideal. Nanoracks and SSL are looking at this as basis for in orbit manufacturing. Add Made In Space to equation and lot possibilities open up.

Ideal? It's as ideal as setting up a machine shop in an old tanker truck on Earth....

To put the alegory in it's context, it is as ideal as setting up a machine shop in an old tanker truck you got for free, instead of buying a brand-new tanker truck and flying it to space...

Still not ideal though

You still need to fly all the people and equipment to space to convert the old tank into a factory or whatever. If those people doing the conversion are going to require a lot of time in space and support equipment, the whole conversion process might require a lot more to be launched into space than the alternative of just launching a module that is already designed and built on Earth to be the desired factory (or habitat or whatever).

Remember, this conversion has to be done in space. Upper stages don't have airlocks or docking ports or anything like that. Are you going to cut a hole in the space for a docking adapter and weld it in place in vacuum in zero-g? Is the structure of the upper stage even going to be compatible with that kind of a change?

It's all far more ambitious than anything that's ever been attempted in space before, and all to avoid a solved problem: just launching something into space that's already exactly the factory or habitat you want.

Yes, there are planty of situations in which this would not be ideal. Generally it is better to reuse upper stages as stages, fit your module on earth, use your lunar lander for return to earth.

But in some situations it may be a better option to use that pressurized volume:Cygnus missions could increase the volume of ISS or the DSG station or DragonLab style missions,On the Moon Xeus landers can be covered with regolith for extra protection.Extra leg room for the @JournyToMars ...

Would it be easier to turn the upper stage into the storage tanks for a propellant depot?Possibly attached to a space station.

That's a lot more plausible than turning it into a habitat or factory.

But I think by the time we have prop depots, expendable upper stages will no longer be a thing. Two well-funded companies have concrete plans for fully-resuable launch vehicles that they are actually actively working on building and testing. Both have flown real hardware. That's far further along than any propellant depot plans, and once fully-reusable launch vehicles are regularly flying, I think expendable launch vehicles won't fly much longer.

Dry storage space itself is already valuable. Maybe things are easier to relocate if there is no need to store them 3 layers deep.

The big problem with wet workshop is that you just get an empty tank and then have to outfit it.I wonder what happens if the concept gets reversed. Start with a rather simple module including all the MMOD and external connections, strip the internals down, using it as tank during launch and reinstall gear on orbit.

Dry storage space itself is already valuable. Maybe things are easier to relocate if there is no need to store them 3 layers deep.

The big problem with wet workshop is that you just get an empty tank and then have to outfit it.I wonder what happens if the concept gets reversed. Start with a rather simple module including all the MMOD and external connections, strip the internals down, using it as tank during launch and reinstall gear on orbit.

I like this idea. But could the normal internal fittings withstand the temperature of Liquid Hydrogen without severe damage?